1. Field of the Invention
The present invention relates to semiconductor devices, and in particular, to a Schottky diode device and a method for fabricating the same.
2. Description of the Related Art
A Schottky diode is a semiconductor device having a metal-semiconductor junction, and a current-voltage character at the metal-semiconductor junction is dependant upon a direction of a voltage applied thereon.
When the Schottky diode is forward biased (i.e. a positive voltage is applied on the anode and a negative voltage is applied on the cathode), carriers can be conducted, and carriers cannot be conducted when the Schottky diode is reverse biased (i.e. a positive voltage is applied on the cathode and a negative voltage is applied on the anode). Thus, the Schottky diode shows a single direction conductive character similar with a conventional diode with a p-n junction. In addition, since the Schottky diode allows single carrier movement, a relatively low threshold voltage and a fast switching speed during switching of forward and reverse biases can be achieved.
Referring to FIG. 1, a cross section of a conventional Schottky diode 100 is illustrated. As shown in FIG. 1, the Schottky diode device 100 includes main components such as an n drift region 104, an anode electrode 112, a cathode electrode 114 and an n+ doping region 116 formed in the n drift region 104. The n drift region 104 is formed in a top surface of a p-type silicon substrate 102, and two spaced field oxides 108 are formed over a top surface of the n drift region 104 to define an anode region 150 and a cathode region 160 in the top surface of the n drift region 104 which are spaced by the field oxides 108. A patterned interlayer dielectric layer 110 is formed over the n drift region 104, covering the field oxides 108 and portions of the top surface of the n drift region 104 and the n+ region 116 adjacent to the field oxides 108. An anode electrode 112 and a cathode electrode 114 made of materials such as titanium, titanium nitride, tungsten, or aluminum respectively covers and penetrates the interlayer dielectric layer 110 to contact the n drift region 104 in the anode region 150 and the n+ doping region 116 in the cathode region 160. A p-type doping region 106 is respectively formed in the n drift region 104 and is adjacent to each of the field oxides 108 in the anode region 150 for preventing a high electric field from happening at the electrode 112, at a region adjacent to the n drift region 104 and the field oxide 108, thereby improving a breakdown voltage of the Schottky diode device 100. A metal-semiconductor junction 120 is formed at an interface of the anode electrode 112 and the n drift region 104 in the Schottky diode device 100.
In addition, for further improving breakdown voltage of the Schottky diode device 100 under a reverse bias, an n-type dopant concentration in the n drift region 104 is normally of not greater than 2.0*1016 atoms/cm3. Such a dopant concentration is helpful for improving the breakdown voltage under a reverse bias but still restricts current spreading per unit area between the anode region 150 and the cathode region 160 when the Schottky diode device 100 is forward biased.
Therefore, a novel Schottky diode device is needed to satisfy high breakdown voltage under a reverse bias and allow high current spreading per unit area when the Schottky diode device is forward biased.